Taylor, 27, dazzled in a stunning maroon dress for her friend's big day at Martha's Vineyard in Massachusetts.
The singer has been friends with Abigail Anderson since the two were at High School together – she even dedicated her 2009 hit 'Fifteen' to their freshman year.
Swift – who wants to move into acting – tended to her friend at the ritzy wedding held on the famous island just south of Cape Cod.
The singer released her new single 'Look What You Made Me Do' earlier this week that slammed Kanye West and Kim Kardashian.
Swift looked stunning in her floor-length gown that had a sweetheart neckline falling into a soft A-line skirt.
The singer – who recently won her groping case – matched the dress color with a bold wine colored lipstick, and sported a soft smoky eye and loose curls to highlight her look.
After the ceremony the wedding party headed to a nearby reception venue where no doubt Taylor serenaded her best friend with a song.
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